1. Field of the Invention
The present invention relates to a satellite multimedia broadcasting (DMB) receiver, and more particularly, to a power control device and method for a satellite DMB receiver, which can reduce power consumption by controlling power according to a reception state of a code division multiplexing (CDM) channel.
2. Description of the Related Art
Recently, standardization and commercialization of a digital audio broadcast is being globally promoted. Europe adopts Eureka-147 as a digital audio broadcast standard and uses a digital audio broadcasting (DAB) system, America uses a digital audio radio (DAR) system, Canada uses a digital radio broadcasting (DRB) system, the international telecommunication union-radio communication sector (ITU-R) uses a digital sound broadcasting (DSB) system, and Korea adopts and uses a digital multimedia broadcasting (DMB) system.
The DAB system has been developed as the next-generation broadcasting system. The DAB system is robust against radio environments and noises in the downtown, and thus makes it possible to receive CD-quality audio signals in a vehicle driving at a high speed although broadcasting signals are transmitted at low output power. Also, the DAB system has expanded the existing audio radio broadcasting concept into an audio/video radio broadcasting concept, and makes it possible to transmit various multimedia information such as news, traffic information, weather information, geographic position information and motion picture information by character and graphic, in addition to a music broadcast.
In the meantime, the DMB system also has been developed as the next-generation broadcasting system. With digitalization of audio broadcasting, the DMB system exceeds the existing AM/FM radio broadcasting system and makes it possible to transmit CD-quality audio signals, characters or graphics and motion pictures at 1.5 Mbit/s, thereby enabling various data services, a bidirectional broadcasting service and a superior mobile reception quality.
The DMB service can be broadly divided into a terrestrial DMB service and a satellite DMB service according to its transmission medium types, and the satellite DMB service can be subdivided into a stationary satellite. DMB service and a mobile satellite DMB service.
The European broadcasting union (EBU) and the ITU-R have recommended the required characteristics of the DMB system as follows:
1. The DMB system should be realized by a digital transmission scheme guaranteeing a high broadcast quality, should be continuously acceptable during the next 50 years, and should provide a high-quality sound of 2 or more channels.
2. The DMB system should make it possible to errorlessly receive a broadcast signal also by a portable terminal in a driving vehicle. That is, the DMB system should enables mobile reception, portable reception and stationary reception.
3. The DMB system should make it possible to provide a PAD (program associated data) channel service for transmitting additional data by a normal broadcast program and a Non-PAD channel service for an independent broadcast program. Accordingly, the DMB system should be able to recognize radio signal data, character data and program data.
4. The DMB system should be high in its transmission capacity and efficiency so as to be able to accommodate various data channel capacities and to increase frequency usage efficiency.
A DMB receiver for the DMB system is also being commercialized. For example, a DMB receiver built in a portable terminal, such as a personal digital assistant (PDA), or a vehicle terminal has been already launched.
In the meantime, a satellite DMB system receives a high-quality sound, various data information (such as traffic information, weather information and game information) and a motion picture (such as a movie and a sports program) from a satellite and then transmits the same to a mobile terminal and a vehicle receiver over a frequency band of 1400 through 2700 MHz.
Such a DMB system transmits one broadcast program on N CDM channels, and each CDM channel is divided into a pilot channel, a program specific information (PSI) channel, a system information (SI) channel and a video/audio channel, and so on.
Accordingly, so as to receive one broadcast program, the satellite DMB receiver is constructed to include N CDM parts and N forward error correction (FEC) parts for receiving the respective N CDM channels.
That is, since one CDM channel is constructed by combination of one CDM part and one FEC part, the satellite DMB receiver should be constructed by N CDM parts and N FEC parts for receiving the respective CDM channels.
Here, the CDM part demodulates a signal outputted from a tuner into a CDM signal, and the FEC part error-corrects the CDM demodulation signal to then generate a pilot payload signal or an MPEG-2 transport bitstream from the CDM demodulation signal according to respective channel characteristics.
Thereafter, the generated MPEG-2 transport bitstream is decoded, whereby a user can view a desired broadcast program.
The so-constructed and operated satellite DMB receiver should simultaneously receive N CDM channels so as to receive one broadcast program, and thus drives all the N CDM parts and al the N FEC parts to thereby consume high power. Accordingly, there is a restriction in a battery usable time of the satellite DMB receiver, whereby the satellite DMB receiver's usable time is undesirably reduced.